1. Field of the Invention
The present invention relates to a disk apparatus and more particularly to a disk apparatus detecting occurrence of short of a spindle motor.
2. Description of the Background Art
In a disk apparatus including a motor for rotating a disk by means of a spindle, a brush (electrode) within the motor wears and debris thereof is produced, which may lead to short of a commutator within the motor. If the commutator shorts out, rotation of the spindle motor stops and hence rotation of the disk stops. When rotation of the disk stops, a control portion such as a CPU (Central Processing Unit) in the disk apparatus attempts to increase a rotation speed of the spindle motor by increasing an output current of a drive IC (Integrated Circuit) driving the motor, and the drive IC generates heat due to a large current. Then, the drive IC malfunctions due to heat generation, a large current flows through an actuator which is a movable portion in a pickup unit in the disk apparatus, and a cover or the like of the actuator may burn. In addition, when rotation of the disk stops, the control portion cannot obtain a normal signal relevant to focusing and tracking. Accordingly, improper control of the drive IC by the control portion leads to a large current flow from the drive IC to the actuator which is a movable portion in a pickup unit in the disk apparatus, and a cover or the like of the actuator may burn.
Japanese Patent Laying-Open No. 08-310414 discloses an electric power steering apparatus capable of ensuring safety of a driver by reliably detecting short-circuiting or break of a signal harness, through which a detection voltage for monitoring a motor current passes, and contact failure of a connector, and by making transition to manual steering. Specifically, motor current monitoring means for monitoring a current that flows through a steering motor and outputting a detection voltage obtained by adding a prescribed offset voltage to a voltage in accordance with the current value is provided. The detection voltage from the motor current monitoring means is compared with predetermined upper limit threshold value and lower limit threshold value. If the detection voltage is out of a range from the upper limit threshold value to the lower limit threshold value, such a condition is detected as abnormal, and subsequent assist power control is prohibited.
Japanese Patent Laying-Open No. 08-310414, however, does not disclose a configuration for appropriately detecting occurrence of short of a motor for rotating a disk.